This comprehensive course will give you the fundamental knowledge needed to begin performing cataract surgery by phacoemulsification and extracapsular removal. Each step from preoperative evaluation to postoperative care will be covered to help prepare you for the operating room.

검토

MM

Excellent for beginners and those who wish to review. A complete package covering all aspects of Cataract Surgery.

DS

May 18, 2020

Filled StarFilled StarFilled StarFilled StarFilled Star

useful topics and all practical problems well covered in course syllabus. Helpful for beginners.

수업에서

Unit 4: Cataract Complications and Extras

This unit covers some additional tools and strategies you will need to manage complications and difficult cataracts. Just like every person isn’t the same, neither is every cataract. Fortunately, we have many tips and tricks that will help you succeed no matter what type of cataract you tackle.

강사:

Elizabeth Du, M.D.

스크립트

Hi there, my name is Dr. Theresa Cooney. And I am a comprehensive ophthalmologist and cornea specialist at the Kellogg Eye Center. And today, I'm going to be talking to you about capsular tension rings. So this is an introduction, capsular tension rings are made of PMMA, a plastic material with a circular open loop ring. These are meant to, Stabilize the zonular apparatus through centrifugal forces. Once they're inserted into the eye, into the capsular bag, they can expand and centrate that capsular bag, supporting weak zonules and recruiting tension from stronger zonules. This in turn will provide intraoperative support for both preoperative or intraoperative zonular defects. And it can also provide long-term postoperative intraocular fixation. It's also thought to potential lead to less and more symmetric capsular phimosis or contraction. So looking back at the history of these rings, back in 1999, Hara et al published article where they discussed a closed silicone ring, but this ring did not adapt to various bag sizes. In 1993, Legler et al published an article where they talked about the first capsular tension ring that was designed for humans specifically. This was an open PMMA ring with eyelets on both ends. And this has since been marketed by Morcher. And we'll be talking more about that later. In 1994, Nagamoto and Bissen-Miyajima implanted an open 12.5mm PMMA ring into a cadaver eye. In 1998, Cionni and his coworkers started using modified capsular tension ring which we will discuss later. In 2002, Dr. Ahmed used a capsular tension segment for the first time. So what are indications for capsular tension rings. The most common indications are for zonular issues. These issues most commonly includes pseudoexfoliation, traumatic zonulysis, iatrogenic zonular damage often incur during the surgery, Marfan syndrome, homocystinuria, hypermature cataracts, high myopia, and post-vitrectomy and/or filtration surgery eyes. It can also be used if there was significant contralateral postoperative capsular phimosis to prevent it in the eye that your operating on. Less common indications include iris defects from things such as aniridia, intraocular neoplasms that have been excised leading some large defects as well as congenital lens colobomas. Other indications that are less common include retinitis pigmentosa, Weil-Marchesani syndrome, and microspherophakia. So what are the criteria for implanting capsular tension rings? First of all, it would be mild zonular instablity as opposed to moderate or severe zonular instability. What this means is that you could have less than not more than 4 clock hours of zonulolysis or mild generalized zonular weakness. And how this can be ascertained as to whether there is some mild phacodonesis or shaking of the lens when you examine the eye. Slight lens movement during the anterior capsulorrhexis creation or mild anterior capsulorrhexis ovalization during creation of the capsulorrhexis. So a person who would have good indications for capsular tension ring placement would be someone with pseudoexofoliaton with a mild floppy capsular bag. Contraindications would be like I said moderate or more advanced zonulopathy. So having more than four o'clock hours of zonular problems and having a capsular bag that anteriorly radializes or posteriorly tears. So you need to have an intact capsule. Because what can happen is the capsular tension ring can provide further extension or breakage of the capsular bag. So there are two major design types of the capsular tension rings on the market currently. The first one is the one that I've highlighted up here. It's the Morcher ring also called the Reform Ring and it is manufactured by Alcon. It has three different sizes or types. The first one is a type 14. This is 12.3mm, and can compresses to 10mm. And it's basically meant for eyes that have axial lengths < 24mm. The most common Morcher ring is the type 14C Morcher ring. It is 13mm, it compresses to 11mm. And it basically is meant for axial lengths of 24 to 28mm, which is the majority of the eyes that we operate on. The third type is a type 14A Morcher ring. This is 14.5mm, it compresses to 12mm. And this is more rigid design from myopic guys that have an extra length of > 28mm. So not used all that frequently. The second design which has come out more recently is the design that I have up here which is the Henderson ring. This is also made by Morcher and it comes in a single size of 12.29 ring that compresses to 11mm. So pretty similar to the type 14C Morcher ring that I have listed above. What they claim is that it has enhanced flexibility and breakage resistance. And that these eight equally spaced indentations that you see along the edge of the ring here allow for easier nuclear and cortical material which can sometimes be difficult when you have to insert a ring at the beginning of a case. Another ring is the Ophtec ring. This is made by StabilEyes AMO, and this is a 12mm ring that compresses to 10mm. And they also have a 13mm ring that compresses to 11mm. But these don't tend to be used as frequently as the Morcher rings. So the device size, how do you decide what is the best ring to put into a person's eye? This is basically often based on capsular bag dimensions. Basically, you want a larger ring for a larger capsular bag. The capsular bag typically positively correlates with both the corneal diameter. So what you want to do is measure the white to white diameter. And then that would basically approximate the compressible diameter of the CTR. And you also want to look at the axial length. You usually are going to need a larger capsular ring size in more highly myopic eyes as I described earlier. It's most effective to have the ring ends to overlap when you're done so the diameter should exceed that of the capsular bag. Many surgeons prefer a larger implant. So the most common ring like I told you before is a 13mm ring that compresses to 11mm. Because if the ends do not overlap, the gap should be opposite the area of zonular dehiscence. So when is the best time to insert a capsular tension ring? It really can be in sort of any time during the case. It can be inserted into the capsular bag or best after a good hydrodissection. If you have to insert it before phacoemulsification, the pros would be that you'd have improved nuclear stability for phacoemulsification during the procedure. So this is helpful for patients with pseudoexfoliation or who have known preoperative zonular issues. However, the cons would be that's more difficult with a mature lens to have this capsular tension ring, and to remove the nucleus, and you can have higher risk of further iatrogenic damage during the case. There's also increased difficulty removing cortical material during the case. And if the capsular tear were to occur, there is a risk that the ring could move posteriorly into the vitreous and that would have to be retrieved later. You can also decide to do it after phacoemulsification. However, if you think you might need it earlier on the case during phacoemulsification or cortex removal, there's also an option of putting iris hooks to support the capsular bag to give you additional support during the surgery. However, there is a risk of the iris hooks could become dislodged and then you could subsequently get some additional capsular tears. But the optimal timing of the insertion is to do it as late as safely possible, and do it any time there's loss of zonular integrity. So what is the technique? Initially, they used to insert this with two hand technique using forceps. Tying forceps were used to inject the capsular tension ring through the wound and the second instrument was used to help direct the insertion. And I will now show you a video that will describe to the more common technique currently which is the injector technique. So basically, the video just showed you a depiction of what the technique is, but now I'll verbally tell you about it. So there's an injector called the Geuder injector and it's a one hand technique. Basically, viscoelastic is used to lubricate the ring when it's placed on the surface of its container. The injector hook is then used to engage an eyelet at the trailing end of the ring, then used to withdraw the ring inside the injector. The injector is then placed to the temporal third corneal incision or the scleral incision whichever you used, and is aimed into the capsular bag after viscoelastic has been placed into the capsular bag of safe. The ring is released slowly under the anterior capsular rim. And the leading edge should be directed against the quadrant of zonular issues so that the implantation is to proceed clockwise. The reason for this is you want to push loose equatorial portions of the capsular bag against the sulcus during the ring introduction, preventing further zonular damage and preventing herniation of vitreous into this area. Once the entire ring is secured inside the capsular bag, the injector is then rotated 90 degrees clockwise. And then posteriorly to disengage the eyelet of the trailing edge of the ring, and then remove from the eye. A few pearls for insertion of these capsular tension rings. It's very important to have a good, but gentle hydrodissection. If you inject for your hydrodissection too vigorously, you could have further issues in terms of further zonular damage as well as causing additional issues with the capsular bag. And this can be done with either balanced salt solution or viscoelastic. You want to circular complete curvilinear capsulorrhexis. And you want to aim for one that is a 5 to 5.5mm size. Again, if there's any defects in the capsular bag whether they be posterior defects or anterior realizations of your capsulorrhexis, it's not safe to use a traditional capsular tension ring. You want to use low settings on your phaco machine. So low vacuum, low aspiration, and low irrigation to try to prevent further disruption of the weak zonules. Chopping is probably one of the better ways to do these cases. And this avoid excessive zonular stress as well as the excessive spinning sometimes you acquire with some other techniques. However, I would recommend that you avoid peripheral chopping initially. And finally, you want to slow irrigation and aspiration. You want to strip tangentially towards the area of zonular dehiscence. Complications I can see. Intraoperatively. Again, you can create further zonular damage and then you have to reassess the situation at that time. As I mention also, the capsular tension ring can become dislocated. And if there's insufficient support in the capsular bag or by the zonules, the capsular tension ring can actually fall into the back of the eye. One way to prevent this from happening is to place a 10.0 prolene safety suture through leading eyelet so that it can be retrieve more readily. Postoperative complications can include subluxation or dislocation of the capsular tension ring at any time. And this is a bigger risk when there's more severe or more progressive zonulysis. So again, it's very important to decide during the case how much zonular damage there is. You can also get posterior capsular opacification from these. But it's actually thought that there might be less opacification that occurs when using a capsular tension ring. And finally, some patients are prone to capsular phimosis or contraction. And there may also be reduced incidence of this compared to when you don't use a capsular tension ring. A few other options, there is something called a modified capsular tension ring which is introduced by Cionni as I discussed earlier. Basically, this has one to two fixation eyelets as you can see over here on the side of the ring that you can fixate anterior to the capsulotomy. And these fixation eyelets are then secured to the sclera and provide additional support to the capsular tension ring. So this allows scleral suture fixation of the capsular bag, but you must have an intact anterior capsulorrhexis and a posterior capsule, again, to be using these. There's also something called a capsular tension segment and that was introduced by Dr. Ahmed as I mentioned earlier. And for these types of segments, you may have disruption of your capsule. And this is used for maximal intraoperative support with scleral fixation. You can place more than one of these as needed. Basically, this chart at the end here, compares the different types of capsular tension, segments, and rings that are available, and tells you what the pros and cons are to both of them. So basically, a continuous curvilinear capsulorrhexis is required for a capsular tension ring and a modified capsular tension ring, but not for a capsular tension segment. It's difficult to place a capsular tension ring and a modified capsular tension ring prior to lens removal, but possible and easier to place a capsular tension segment just because they're smaller. The only ones that can be used with anterior capsular tears and posterior capsular rents are the capsular tension segments. The capsular tension ring can be used with less than 4 clock hours of zonular dialysis. Or as the capsular tension segment and modify capsular tension ring can be used to > 4 clock hours. Again similarly, for those cases I have progressed on your zonulysis, a capsular tension ring should not be used, but a modified capsular tension ring and capsular tension segment can be used. These latter two devices can also be used as sclera fixated sclera. One of the things both the capsular tension ring and modified capsular tension ring are pretty easy to remove from the eye if necessary whereas the capsular tension segment is not as easy to remove. And finally, the capsular tension ring and modified capsular tension ring make cortical removal a little bit difficult because of the bulkiness of them. Whereas the capsular tension segment is less bulky and it's there for easier to remove cortical material. And this is just some of the references that I used for this presentation.